The present invention relates to methods and devices used to monitor the activity of a living subject such as a human patient. More particularly, the invention relates to patient monitoring systems that have multiple sensors with corresponding cables or similar communication links that are connected to monitoring equipment.
Patient monitoring systems generally include a plurality of specialized sensors. Each sensor is designed to measure a specific activity and generate a signal representative of that activity. The signals are transmitted over cables or similar signal carriers to monitoring equipment that processes the signals and generates an output, often in the form of a multiple-component graphical image that is displayed on a monitor such as a CRT, flat panel display, or similar device. A typical patient monitoring system may include many sensors and associated cables. The sensors used might include a blood pressure sensor, a blood oxygenation sensor, an ECG (electrocardiogram) sensor, a respiration sensor, a temperature sensor, and a thermodilution cardiac output (CO) sensor.
Generally, information from the sensors is recorded in a large, usually stationary monitoring device. This method of storing information poses a problem when a patient must be moved. Because a stationary monitoring device is not readily moved, moving a patient requires disconnecting the numerous cables from the device. This interrupts monitoring of the patient. In order to maintain patient monitoring, the patient may be connected to a portable monitoring device. This requires reconnecting the numerous cables to the portable device. This is not an easy task and often results in a tangled mess of cords (sometimes referred to as xe2x80x9cspaghettixe2x80x9d). Of course, even when connected to a portable device, information from the period of time when the patient was not connected to either the portable unit or the stationary unit is lost. Trend data from the stationary data device is also lost. Lastly, since there presently is no way to transfer such data automatically, patient identification data must be manually reentered into the portable device.
Other difficulties associated with moving a patient and monitoring his or her biological activity relate to the portable monitoring devices themselves. Portable units are generally difficult to use and expensive. Cost is a large problem because capital equipment ownership is generally assigned on a department-by-department basis. Thus, transferring portable equipment from one department to another within a care facility often causes administrative difficulties. In addition, some portable units are less than satisfactory because of their small monitor size and limited capabilities. Thus, there is a need for improvements to patient monitoring systems that permit patients to be moved with less difficulty and loss of data.
The present invention provides a relatively easy and low cost method and apparatus for reducing the loss of data when moving a patient from one monitoring device to another. The invention may be implemented in a cable management and data acquisition system that is designed to be coupled between the leads from activity sensors and a patient monitoring device. The cable management and data acquisition system has a housing with one or more connection ports. Each port is designed to be connected to activity sensors, such as ECG sensors, blood pressure sensors, temperature sensors, and the like. The connection ports receive the information from the sensors and deliver it to a device interface. The device interface is coupled to a non-volatile memory, which is used to store patient data and data from the sensors. The device interface is also connected to an output port through which the device interface sends data to a monitoring processor and from which the device interface receives commands. Preferably, the device interface is an application specific circuit and communicates information according to a serial data bus protocol. Data from the sensors is converted to a digital format, as necessary, by an analog-to-digital converter coupled between the connection ports and the device interface.
The size of the memory in the system can be changed depending on the end use of the system. If a user requires storage of trend data and histories, the system is equipped with a relatively large memory. The system is equipped with a smaller memory when monitoring other types of information. Regardless of the size of the memory used, the system uses the same scheme to access data in the memory.
The invention provides a method of storing patient data. The method includes gathering data from at least one sensor, generating a write command with a monitoring processor, and processing the write command in a signal processor. The method also includes locating a non-volatile memory outside the sensor and outside the monitoring processor. Once the write command is processed, the command is executed through the device interface and the gathered data is stored in the non-volatile memory.
Preferably, processing the write command includes the act of breaking the command into command packets. The command packets are then assembled during the processing of the write command. Each command packet typically includes a start-of-packet field, a command field, and a check field. The command packet may also include a data field.
The monitoring processor includes a digital signal processor that has a message program or package that includes a request message sub-package and an algorithm sub-package. The request message sub-package concatenates message packets and validates the address and format of message packets. The message algorithm sets bus commands from a command table to perform the required read or write operation.